Tuning the Fretboard

No, you don’t need new glasses: This is a 4-string fretboard equipped with True Temperament frets.

The fretboard: It’s where we focus most
of our practice time and that means we
stare at it a lot. It’s interesting how today’s
fretboards look exactly the same as in the
old days. We’ve seen some changes in fretboard
radius over time, but even the fret
material has remained consistent for the
vast majority of instruments. True, we now
have stainless steel frets, which were developed
to reduce fret wear, but most manufacturers
don’t push this material, as it’s way
harder to work with than standard fretwire.

What bassists have used for decades is
a ’board with straight frets, and fret position
is calculated using a constant divisor.
This way, the 12th fret ends up exactly in
the middle of our scale length. The math
behind this divisor is very accurate and
the system seems to work well—after all, a
lot of great music has been made with it.
(Note: We’re not talking about different
tunings. This discussion is all about getting
accurate pitches in standard tuning.)

The mathematic model behind fret
distances is an approximation of an ideal
string. We have to make some shifts from
the ideal to accommodate real-world
parameters, and one of these parameters is
the stiffness of the string. The further we
reach up the fretboard, the more this plays
a role in the resulting pitch. Another factor
is mass and whether a string is wound or
plain, although plain strings are something
that only a few extended-range bassists will
ever have to deal with.

On a traditional fretted instrument,
our only key to adjusting intonation is the
bridge, and it can only do one compromised
adjustment for the entire scale length. The
result is that our intonation will only work
well for a certain area of the fretboard.

You could say that the system works fine
the way it is, but some creative minds have
come up with interesting ideas that at least
shed some light on our workspace and its
limitations. Most of these ideas initially
focused on the guitar market, as a guitar’s
higher notes show the effect of various systems
more prominently, but when it comes
to stiff, heavy, and thick strings, well, we
own that world. Let’s look at a few of these
ideas for improving intonation.

The Earvana nut. These replacement
nuts are easy, non-permanent mods that
offer an alternative intonation system.
The principle is that the nut is no longer
straight, and it provides a compensation
that’s similar to the bridge. The nut position,
and therefore scale length, is slightly
altered for each of the strings.

Once a non-straight nut is installed, the
bridge will need a new setup. This mod
makes the biggest difference in the range of
the first frets. Claims that a compensated
nut works over the entire range seem to be
a bit over the edge and probably depend on
how closely you look at the data, but this
technology surely helps overall intonation.

The Circular Fretting System. The
idea behind the Circular Fretting System
(C.F.S.) is that the strings, coming from
the nut, are not parallel. They are indeed
slightly divergent, and on a 4-string bass,
the outer strings are shifted sideways about
10 mm. That means that the outer strings
“see” a slightly larger scale length.

To compensate to an equal scale and
make all strings cross the fret at an exact
angle of 90 degrees, the C.F.S inventors curve the frets. Installing curved frets
involves way more work than classic straight
frets, so let’s look at the inventor’s claims to
weigh the benefits. For starters, it’s claimed
the equaled scale will make an “extremely
accurate pitch” and “sharply defined tone.”
The exact 90-degree crossing delivers a
“longer sustain, sonorous harmonics, bell-clear
sound, and a fast resonance.” Sounds
like it’s worth the additional work to install
curved frets.

Here are the numbers for a traditional
34"-scale bass: The additional scale length
of the outer strings is 0.002" or 0.06 mm,
and the strings cross the frets at an angle
of 89.9998 degrees, instead of exactly 90
degrees. But because even the most accurate
fingering will generate bigger variations in
this angle, there will be no intonation benefit
to having an exactly equal scale length
for different strings. Also, the aforementioned
divisor still generates the same inaccuracies.
And every slightly bent note on
any fretboard would, to use circular fretting
terms, create a less sharp tone and impact
the harmonics and sustain. Somehow this
conflicts with experience.

True Temperament fretting. At first
sight, this is pretty wild! It represents the
most laborious fretwork one can do, as it
keeps track of the real pitch of each and
every note on the fretboard with a corrected
fret position, and almost none of the frets
remain straight. Additionally, the Swedish
company behind this technology produces
fretboards with a variety of temperaments,
including 12-tone equal, Wohltemperierte
Gitarre, Thidell Formula 1, low-tune guitar,
and bass guitar. Each of these serve a special
purpose and is a world of its own.

Alternative intonation systems can
inspire you to dig deep into the tradition
and evolution of musical instruments. It’s a
fascinating journey, but for not everyone—in fact, some players love their basses for
their impreciseness. A final thought: If you
chose to explore this sonic world, you’d better
convince your guitar-playing bandmates
to do the same.

Heiko Hoepfinger is a German
physicist and long-time bassist, classical
guitarist, and motorcycle enthusiast. His
work on fuel cells for the European orbital
glider Hermes got him deeply into modern
materials and physical acoustics, and
led him to form BassLab (basslab.de)—a
manufacturer of monocoque guitars and basses. You can
reach him at chefchen@basslab.de.

Heiko Hoepfinger is a German physicist and long-time bassist, classical guitarist, and motorcycle enthusiast. His work on fuel cells for the European orbital glider Hermes led him to form BassLab (basslab.de)—a manufacturer of monocoque guitars and basses.

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